Multistage pump or motor



June 20, 1939. F a. K. BENEDEK 2,153,030

MULTISTAGE PUMP 0R mo'roa Filed July 16, 1955 5 Sheets-Sheet 1 ELEKKEJENEDEK- if! HUM/MM June 20, 1939. K. BENEDEK 2,163,080

Q Muunsnem PUMP 0R o'roa Filed July 1a,. 1935 5 Sheets-Sheet 2 0. ,lnobo June 20, 1939. v E K 2,163,080

MULTISTAGB PUMP OR MOTOR Filed July 16, 1935 5 Sheets-Sheet 3 IELEKKEIENEDEK- Patented June 20, 1939 UNITED STATES PATENT OFFICE MULTISTAGE PUMP R MOTOR Elek K. Benedck, Bucyrus, Ohio Application July 16,

- 4 Claims.

v vention is to provide a transmission mechanism capable of delivering substantially constant powtorque delivery cycle so that a substantially continuous and stepless application in speed and torque are efiected.

Another object is to produce a reversible motor so that the range of' operation may be effected in either direction of rotation selectively.

A more specific object is to provide a motor for this purpose comprising a plurality of stage units, each unit being of economical design for its critical speed range, and the units being so related to each other that the effective high efiiciency range of each overlaps that of, the other in a manner such that the total average .value of efficiencies will efiect a substantially constant power delivery for a constant input of power, at the highest efficiency for which each hydraulic motor, as now designed, .is inherently capable when operating at its critical speed and in which each motor will deliver the major portion of the constant power to be transmitted by the entire machine while operating in the region .of its critical speed.

Correlative specific objects are to provide a multi-stage motor for power transmission in which each of the stage units dominates the power of the combination at the instantaneous or critical speed range and throughout the high emciency range of the particular unit, and in which each unit is of economical design fora critical speed range in which the unit dominates the power which is to be transmitted.

Another specific object is to provide for both mechanical and hydraulic disassociation of the units from each other throughout certain portlons of the range of operation whereby the dommating unit is not subjected to losses which might otherwise be occasioned by the other units.

A correlative specific object is to provide for 1935, Serial No. 31,651

automatic disassociation' of the stage units for this purpose in either direction of rotation of the multi-stage pump or in both directions of. rotation thereof.

Another object is to reduce the frictional and hydraulic losses between the plungers and cylinders of the stage units and the crossheads and the corresponding reactances by an improved load and torque transmission therebetween.

Another object is to provide a structure in which a combination of capillary and centrifugal force feed lubrication'combined with rolling load transmission is afforded between the plungers and the associated reactanc'es.

Another object is to provide for efiicient axial thrust means between the stage units of the motor.

Other objects and advantages will become ap parent from the following specification wherein reference is made to the drawings in which Fig. 1 is a horizontal longitudinal sectional view of va multi-stagepump or motor embodying the principles of the present invention;

Fig, 2 is a vertical cross sectional view of one of the motor units and is taken on a plane indicated by the line 22 in Fig. 1;

Fig. 3 is a fragmentary sectional view taken on a plane indicated by the line 33 of Fig. 1, the plunger and reactance block being shown in elevation for clearness in illustration;

Figs. 4 and 5 are respectively an end elevation and axial sectional view of the one of the rollers of the reactance support and plunger head connection;

Fig. 6 is a horizontal longitudinal sectional view of a motor such as illustrated in Fig. '1, the stage units thereof being separate units, connected by overrunning clutches for eflfecting concurrent or individual drive therebetwe'en;

Fig. '7 is a fragmentary vertical sectional view taken on the plane indicated by the line 1-1 of Fi 6;

Fig. 8 is a fragmentary horizontal sectional 'view of two adjacent stages of a motor such as illustrated in Fig. 6; showing, between the units, a modified clutch connection operable by the centrifugal force of its respective unitin either direction of the rotation of the particular unit; Figs. 9 and 10 are vertical cross sectional views taken on planes indicated by the lines 9-9 and Ill-l0 respectively of Fig. 8;

Fig. 11 is a fragmentary horizontal sectional view of two adjacent stages of the motor illustrating another modified clutch connection there between taken on the centerline of the pintle;

Fig. 12 is a vertical sectional view taken on the plane indicated by the line I2I2 of Fig. 11;

Fig. 13 is a fragmentary sectional view in a radial plane of the motor illustrating a modified connection between the plunger head and reactance means;

Figs. 14 and 15 are respectively a side elevation and an end elevation of a combination coupling bolt and plunger reactance roller. support;

Fig. 16 is a longitudinal sectional view of the elements of Figs. 14 and 15, as a sub-assembly unit with capillary rollers therebetween;

Fig. 17 is a cross sectional view taken on a plane indicated by the line III'I of Fig. 16;

Figs. 18 and 19 are respectively a side elevation and bottom plan view of the reactance block illustrated in Fig. 3;-

Fig. 21) is a side elevation of one of the coupling means between a segmental thrust block and a reactance ring;

Fig. 21 is a diagrammatic illustration of the pintle showing a fluid circuit which may be utilizedin the present invention;

Fig. 22 is a graphical illustration of a power transmission cycle showing the range of speed at which the transmission delivers constant power and the range of underspeed and overspeed at which the transmission may operate at decreasing power with additional speed and torque characteristics;

- Fig. 23 is an efilciency diagram showing broadly the functional relation between power output and efliciency in hydraulic pumps .and motors and the efficiencies of plurally different size units when operated simultaneously or separately;

Fig. 24 illustrates the functional relation between the speed and the torque developed by a hydraulic motor operating to deliver constant power throughout the 'entire range. of speed;

Fig. 25 illustrates the fimctional relation between the efliciency and the eccentricity, or stroke, in a given size pump or motor;

Fig. 26 illustrates a characteristic functional relation between the e'fliciency and the stroke, the efficiency being shown as a function of the specific size per horsepower of a pump or motor constructedaccording to the present invention;

Fig. 27 is an efiiciency curve illustrating broadly the characteristic that peak efllciency of a unit is attainable at one point of the speed scale only, which will be termed as critical speed, and that the efllciency remains substantially constant in the region of critical speed; and,

Fig. 28 illustrates generally. the functional recifically that maximum efliciency is attainable only at one certain stroke-cylinder diameter ratio. A 1 Referring to Figs. 1 to 3 inclusive,- the motor shown for illustration-of the inventioncomprises opposite end thereof so that the fluid circuit may the motor section of a hydraulic transmission, the

pump portion of which, not shown in Fig. 1,. but

shown diagrammatically in Fig. .21, may cooperate with' the same pintle as the motor but at the be self-contained by provision of suitable ducts within the pintle. The motor proper ismounted within a casing I comprising a cylindrical shell having an integral end wall 2 and being closed at the opposite end by an end plate 3, which,

in the transmission, is a part of the division wallbetween the pump and motor sections. The casing, for economy and simplicity in design and for efliciency, is formed in a plurality of coaxial portions Ia, Ib, and I0 respectively, each of which is of a different diameter from the others for snugly accommodating different size motor stage units. For purposes later to be described, the

.largest diameter portion Ia of the casing is adjacent the plate 3, the remaining portions being of less diameter successively toward the opposite end wall 2.

Rotatably mounted within and coaxial with the casing I is a cylinder barrel, designated generally as 5, whichis formed in three integral stage portions or units 5a, 5b and 50 respectively, the unit 5a being the largest, and the remaining portions being'successively less in diameter in the order enumerated so as to conform generally in size with the casing portions Ia, Ib and lo in anti-friction ball or rolling bearing elements I l and I I respectively. The outer races of the bear.- ingsJfl and II are correspondingly mounted in internal peripheral shoulders in the end plate 3 and end 'wall 2 respectively, and cooperate therewith for constraining the barrel to fixed radial and axial position within the casing. Adjustment of the bearings for axial slackness resulting from wear may be effected by adjustment of the plate 3 axially, this adjustment being made by interposingv suitable shims between the end wall of the casing portion Ia and the marginal portion of the plate 3. The barrel is sufllciently rigid between the bearings I0 and I I to resist deflection due either to hydraulic load or to stresses caused by torque load: On the smaller end of the barrel is a driving orgirnpeller shaft .I2 which, for economy, may be made integral with the barrel hub I. 1

Each of the barrel portions 5a, 5b and 5c comprises a separate and distinct motor unit.

The units have a plurality of circumferentially spaced radial cylinders I4, I5 and. I6, respectively in the order enumerated, which, through suitable radial ports I8, I9 and 20, respectively, communicate with a common axial pintle bore in the barrel for valving cooperation with a suitable valve pintle 22.

The valve pintle 22 is mounted by a shank portion 21 in the end plate 3 of the casing and extends into the casing coaxial with the barrel. The pintle .comprises a plurality of valve portions 22a, 22b, and 220 respectively. These valve portions are of different diameters, corresponding to the different size of the unit with which each is associated. correspondingly the bore of the barrel 5 comprises a plurality of different diameter valve portions corresponding to and snugly .fltting respectively, the pintle valve portions rollers 26 for providing therein a combination high pressure oil and roller combination bearing.

correspondingly at the opposite or free end of the pintle, a raceway 21 is provided in which are accominodated capillary cageless needle rollers 28. The needle rollers 26 and 28 engage corresponding radially aligned portions of the wall of the barrel bore for accurately positioning the pintle therein and spacing the pintle with the proper slight clearance for insuring, the formation of capillary oil films between the barrel bore wall and pintle, entirely around each pintle portion. In this manner hydrostatic balance of the pintle may be effected in a manner latertp be described more fully.

The valveportions of the pintle and corresponding portions of the barrel bore wall are tapered slightly toward the small'or free end of the pintle so that by slight axial adjustment of the casing portion I toward the end plate 3, wear between the cooperating valve wall portions of the pintle and barrel bore may be compensated. Each of the pintle valve portions is provided in the zone of the corresponding cylinders with reversible valve ports, either of which may be the high pressure port and the other the low pressure or suction port. In the form illustrated, and for convenience in description, the high pressure ports are designated respectively as 30, 3| and 32, the low pressure portsbeing designated 34, and 36 respectively.

-Within'the pintle are longitudinal ducts 38 which are tapered to smaller diameter gradually from the shank portion of the pintle toward the smaller end thereof and which are in communica-' tion with the ports 30, 3| and 32 respectively, thus connecting the ports in parallel with each other. The ducts 38, in turn, communicate with a main reversible high pressure-port 48, formed in the pintle, through which port the pressure fluid is introduced from a suitable source for operating the motor. In those instances in which the motor utilizes the common pintle, as described in my copending application, Serial No.

. 22,259, filed May 18, 1935, the ducts 38 extend beyond the port 40 and to suitable reversible ports of the pump end of the pintle. correspondingly, in the pintle are return'ducts 4| which communicate with the ports 34, 35 and 35, connecting these ports in parallel. The ducts 4| in turn, communicate with a main reversible return port 43 through which fluid is discharged to a suitable sump or, in the case of a pump utilizing the same pintle, to the cylinder inlet port of the pump, directly through the pintle. Thus upon introduction of fluid pressure through the main port 40, all of the units 5a, 5b and 5c are connected in parallel with each other and with the source of pressure fluid.

If desired, the ducts 38 may open through-the free end of the pintle into the barrel bore which is sealed against the discharge of pressure so as to form a dead end bore or pressure fluid chamber 45, so that the line pressure may beutilized for balancing the pintle hydrostatically by supplying from the chamber 45 an annular oil fil over the free end of thepintle.

Referring next to the plunger assemblies used, each set of cylinders l4, l5 and I6 'carries'a corresponding set of plungers 50, 5| and 52, which plungers cooperate with a suitable reactance means later to be described, for rotating the barrel. Since the plungers of the various stage units are the same in form and function, with the exception of slightly different plunger head engaging means in'the larger stage, the plungers in. stage unit 5b only, illustrated in Fig. 2, will be described in detail.

Each of the plungers 5| is provided with a crosshead 52 extending tangentially of the .path of travel of the associated plunger. Surrounding the barrel portion 5b'is a reactance means which is adjustable for controlling the stroke and reversing the ports of the associated units independently from the other units.

The reactancefor the stage unit 5b includes a suitable stator or stationary reactance member 53 which comprises a ring having on its outer surface enlarged sliding bearing surfaces 54 at diametrically opposite sides. These surfaces cooperate with sliding bearing abutment surfaces 55 in the casing portion lb for supporting the stator. 53 with its axis parallel to the barrel axis while rendering it adjustable to reverse the ports and adjust thestroke of the associated plunger.

roller elements 58 may float together axially thereof.

Mounted on the ring 51 are spacedparallel matched rings 59 having inset radial annular shoulders at their radially outer margin and axial annular shoulders extending inwardly therefrom. The rings 59 are positioned on the ring 51 with the shoulders of the rings 59 engaging the inner marginal surface of the ring .51 and the end walls thereof so that the rings -5 9'and 51 form a rigid structure of U-shape'd cross section, as better illustrated in Fig.1. This rotary reactance structure, therefore, forms a deep =annular trough opening toward the axis of rotation.

The plunger crossheads 52 are provided at their lateral limits-with parallel, radial, smooth faces and the adjacent. faces of the rings 59 are correspondingly formed flat and"parallel to each other, and being spaced apart only sufliciently to receive the heads 52 with operating clearance therebetween. Interposed between each plunger head 52 and the ring. 51 are segmental thrust blocks 60 which are better illustrated in Figs. 18 and 19. One such thrust block is provided for each plunger head and comprises a cir cular segment, the arcuate wall designated 6| being of the same radius as the ring 51 so as to fit snugly resting on the ring 51, they are retained in place,

but are free to adjust themselves slightly circumferentially of the ring in each direction by relative sliding between the arcuatesurfaces 6i 'and'the rings 51. Very slight operating clear- .ance is provided between the side walls of the blocks 60 and rings 59. For purposes later to be explained more fully, each groove 63 accommodates a set of capillary cageless needle rollers 64," the rollers having their axis parallel tothe axis of rotation of the barrel, so as to reduce the frictional resistance between the plunger head 52 and chordal wall .62 of the associated seg-'- mental block, as the plunger head oscillates therealong to compensate for tangential components of eccentricity. The needle rollers-64 have a total clearance parallel to the slot such that each roller may be spaced only a capillary distance from the adjacent rollers.

For insuring proper cooperation between the plunger heads and the segments SI! and for transmitting torque and assuring positive operation of the plungers on the low pressure strokes, the inner wall surface of the heads 52, at portions adjacent the ends of the heads, are undercut, as indicated at 65, the undercut portions having bearing surfaces parallel to the outer or block engaging wall of the head, and suitable means engage these walls of the undercut portions for the operation described. Here it should be noted thatv by undercutting the end portions of the plunger heads inthis manner, smoother flexibility of the head is obtained and the reactance elements for engaging the undercut portions may be disposed closer to the axis of the associated plunger so as not to interfere with radial clearance between the reactance means and the barrel while permitting a reduction in the overall radial dimensions of the motor.

The reactance elements for this purpose per form a dual function of securing the rings 59.

together and in cooperation with the ring 51 and at the same time rollingly engaging the under surface of the plunger heads 52.

Referring to Figs. 1 and 2, at each undercut portion of the head there is provided a sleeve roller 66 which is in rolling engagement with the undercut surface, preferably with slight clearance. The roller sleeves 55, in turn, are mounted on crosspins or bolts 5'! which-thus form part of the reactance elements of the plunger heads.

. The rings 59 are provided with sets of aligned bores in each aligned pair of which is mounted one cross bolt 61. Each bolt -is'provided at one end with an enlarged head portion and at'the other end with a screw threaded portion, one bore of each aligned pair having a complementary counterbore for the bolt head and the other. having a screw threaded portion. Thus the rings operate with the bolts 61 to secure the rings 59 together. In this manner the bolts perform a dual function as operating crosspins and connecting means for the reactance rings. Accordingly, the number of working parts is considerably reduced.

With the plunger and reactance assembly in the cooperative relation described, several advantageous results are obtained ,aside from the reduction of the number of .working parts. First, each plunger head 52 is anti-frictionally mounted for cooperation with its-corresponding segmental block 60. Due to the sleeves 66 and.

this anti-friction mounting, complete anti-friction load and torque transmission between the reactance rotor and the barrel is eifected. Allofthese parts lie within the radial trough formed lubricant thereto. This lubricant, since all partsremain' within the trough, is under high pressure due to centrifugal forces and thus high pressure oil films are formed between the sleeves i and the pins 61, between the sleeves and the undercut walls 65 of the associated crosshead, between the outer wall of the crosshead and corresponding cooperating wall of the segmental block I and finally between-the arcuate outer wall of the block 50 and the inner wall of the ring 51.

films are also maintained on'the side walls of these parts. Due to the trough 63 and the needle rollers 64, a most efllcient bearing is pro- Such vided at one of the points of greatest frictional loss in the usual T-head plunger design of pump or motor.

First, a high pressure oil film bearing is provided-due to centrifugal forces alone. This high pressure oil film is augmented due to the capillary action of the needle rollers 64. A rolling friction between the head and segment is provided by the needle rollers themselves but this rolling friction is on rollers which, themselves,

/ roll on oil films instead of in metal to metal contact. This, in turn, is due both to the centrifugal force and the fact that the needles are spaced a capillary distance apart with the result that the film is rendered highly tenacious. Again, due to the capillary needle rollers, instead of a few points of contactbetween the head 52 and block 60, the load reactance is applied to the head in a manner such that it is uniformly dis-- load capacity more than tentimes greater than I commercial bearings is provided.

In order to shift the stator 53, suitable control rods Illb are connected to the stator at diametrically opposite portions and extend parallel to the planes of the supporting bearing surfaces 54. The rods 'lllb extend through suitable bores in the casing portion lb for adjustment either manually, or by suitable hydraulic pressure controls, from the outside of the casing, suflicient clearance being provided between the bores in the casing wall and the rods 10b to permit free operation thereof and prevent binding of the rods and consequent misalignment or ineflicient operation of the stator. In order to limit the maximum and minimum strokes of the unit, suitable limit [stops II are formed on the outer surface of the stator and engage complementary accurately machined abutment stops 12 on the interior of the housing portion lb when the stator is shifted to either extreme. These stops are so positioned that they prevent movement of the stator beyond a predetermined extreme strolre position or to stalling position. The stators of the large stage unit In and small stage unit 5c correspond in general structure and operation to the stator 53 and are similarly mounted and are provided with control rods-Illa and 100 respectively, corresponding to the rods 10b.

Referring next to Fig. 3, there is illustrated a plunger and block of the largest unit 5a. in which the segmental blocks 14, corresponding. to the blocks 60, are provided, and in which each plunger 50 is provided with a head 15 corresponding to the head 52. Since the barrel portion 5a produces I to the fluid under hydraulic pressure.

the greatest torque and consequently may create or be subjected to higher stresses which might tend to bind the sleeves 66 on the crosspin 61, or greatly increase the frictional resistance therebetween, the sleeves I6 are" provided. The sleeves 16 are mounted on the connecting cross bolts TI on capillary cageless needle rollers I8, which likewise maintain capillary oil films and are subjected This structure assures highly eflicient cooperation between the crosspins or bolts and the associated plunger head.

Referring next to Fig. 13, a slightly different mounting for the plunger crossheads is provided in which the speed of oscillation of the contacting surfaces of a crosshead and its cooperating thrust segmental block are reduced. In this structure; the reactance ring accommodates a segmental block 8| corresponding to the block 60. The block 8| is restrained from displacement circumferentially of the ring 80 by a pin 82 which engages a suitable bore in the block 8| with slight clearance radially of the pin so that'the block 8| is free to float radially of the ring 80 but is constrained to comparatively narrow limits of movement circumferentially of the ring 80. The thrust block 8| is likewise provided at its chordal face with a flat surface between the ends of which is a groove 83, corresponding to the groove 63 of the block 60,

in which are provided capillary cageless needle rollers 84, with proper clearance for capillary action between adjacent rollers. The plunger 85 has a plunger head 86 corresponding in general to the head 62 but having a groove 81 on its outer face corresponding in length tangentially substantially with the groove 83. In this groove also are provided capillary cageless needle rollers 88, spacedfor capillary clearance only therebetween. Interposed between the block 8| and the head 86 is a floating block 89 having parallel inner and outer faces and which operates to transmit load and reactances between the block 8| and head 86. Thus upon oscillation of the head 86 relative to the block 8|, though the relative speed of oscillation of the block 8| and head 86 remains the same, the block 89 automatically centers itself, by float ing so that the relative speed between the block 89 and the block 8| and between the block 89 and head 86 is one half of the relative speed between the head 86 and block 8|. Next, both the head 86 and block 8| roll on needle rollers 84 and 88 respectively, with respect to the block 89 and the needle rollers are free .rolling and cageless. Therefore, the needle rollers of each set roll along the block 89 at one'half the speed of the head 86 and the block 8| relative to the block 89. Consequently the relative speed between the head 86 and block 8| is so divided among the sets of needle rollers and block 89 so that the speed of the surfaces of the'block- 8| and head 86 relative to the means transmitting load thereto and in direct contact therewith is only one fourth of the relative speed of the head 86 and block 8| As will more fully appear hereinafter, it is often desirable for the highest efficiency that no one of the motor or pump units be subjected to a drag resulting from resistance in the idle units. In pumps and motors of this character, economical design dictates that the stages be of different size, the high torque, low speed being the largest stage unit, and the high speed, low torque being the 4 smallest stage unit. The capacity of the large stage is necessarily much greater thanthe small stage as also are the forces and resistance to rotawhen the stroke of the large stage is materially reduced near the lower limit. In such instance, a small high speed unit would utilize most of its power in overcoming the drag of the large unit. Furthermore, where the large unit is rotated at speed which the small unit can withstand, due to its light structure, the large unit would be subjected to dangerous centrifugal forces. On the other hand, the large unit may operate at high efiiciency even when overcoming the resistance and frictional losses of the small unit as centrifugal forces and resistance in the small unit are then so dominated by the large unit as to be practically negligible and the frictional losses also are small in comparison to the power of the large unit.

In order, therefore, to render the'smaller units successively free from restraint by the larger, overrunning clutch connections may be provided between the units as illustrated in'Figs. 6 and 7. In this particular structure, the parts correspond in form and function to the parts described in connection with Fig. 1, with the exception that the barrel is divided into separate and independent units I05a, I05!) and I050 of progressively less diameter inthe order enumerated, and the needle rollers I58 between the stator and'rotary reactance are accommodated in a circumferential groove in the stator I53. The groove provides a trough opening radially inwardly so that centrifugal pressure lubrication is retained and true capillary cageless needles are not necessary. Each of these barrel portions cooperates with a corresponding portion of the pintle I22. The torque transmitted by the motor is transmitted through the shaft 2 on the small barrel unit I05c, all of the barrel units being sufiiciently strong for torque transmission from the largest unit I05a. Inter-' posed between and accurately spacing the barrel portions axially are sets of axial thrust bearings I06 and I0! respectively which operate in aligned grooves forming raceways in the adjacent end portions of the barrel units.

Referring first to the barrel portions I05a and I05b,'overrunning clutches are provided therebetween so that the barrel unit I051), when operating at higher speed than the barrel unit I05a, is entirely disconnected therefrom but when, for any reason, the speed of the unit |05a becomes esual to or greater than that of M51), the barrel units are mechanically interlocked for rotation therewith. A simple and effective overrunning clutch for this purpose is illustrated in Fig. 7 and constitutes a series of short tangential grooves I08 formed in the end wall of the unit I05a. The groove is of decreasing depth in a direction opposite to the direction of rotation of the unit I05a. At the corresponding end of the unit |05b is an abutment surface I09 which lies substantially in the plane of the end wall of the unit I050. Within the slot I08 is a ball bearing 0 which is retained therein by the wall I09. The groove is of suflicient depth at its deeper end so that the ball may be accommodated therein without contact with the wall I09 and the depth of the groove decreases in a direction opposite to the direction of rotation of the unit |05a an amount sufiicient to cause the ball to wedge tightly between-the bottom wall of the groove and the wall I09 of the unit I05b when disposed in the shallow end of the groove. Therefore, if the unit I05b is driven or rotates in the direction indicated by the arrow in Fig. 7, relative to the unit I05a, the ball rolls to the deeper end of the slot I08, thus disconnecting the unit I05b from the unit I05a. If, however, the

unit' M511 is run at greater speed than the unit I051), or if the unit Ib is idle, the relative rotation disposes the ball I III in the shallow end of the groove, thus mechanically interlocking the barrel units for rotation together. Obviously, a heavy axial thrust is exerted by this action but this is resisted by the thrust bearings I 06 and III1 and the combination bearings H5 and 6,.

which mount the barrel as a whole in the casing. Such a clutch, however, does not provide for disconnection and connection except in one direction of rotation of the barrel. A similar overrunning clutch utilizing a ball III is interposed between the small barrel portion H151. and the opposite end of the barrel portion III5b.

In many instances it is desirable that the motor be reversible, however.

Referring to Figs. 8 to 10 inclusive, a centrifugally operated clutch is provided between the barrel stage units which will operate in either direction of rotation. Since, aside from the clutch elements themselves, the structure is the ing the necessary high pressure oil films and anti-friction mounting of the blocks being interposed between the guideways. and the ends of the block I21. Obviously, under centrifugal forces, each ,block I21-will move outwardly, radially in the-guideways. The force required to move the block I21 radially outwardly depends to some extent on the mass thereof but may be accurately and positively controlled by a suitable spring I29. The spring I23 is mounted'at one end in a suitable screw plug I30 in the portion of the flange I25 which bridges the outer ends of the guideways. The opposite end of the spring I23'abuts the block I21. By adjustment of the spring or by provision of a spring or other resilient means of the desired strength, the rotational speed of the barrel at which the block will move radially outwardly, may be accurately controlled and when this speed is decreased below the proper limit, the spring may operate to return theblock inwardly to the position illustrated in Fig. 9.

Mounted in a suitable bore in the block I21 and extending parallel to the axis of rotation is a clutch pin I3I, one end I32 of which projects outwardly axially beyond the wall of the flange I25 adjacent the barrel unit III5a'. On the side wall of the barrel unit III5a' there are provided a series of lugs I33 spaced apart circumferentially and in alignment axially of the motor with the pin I3I when the pin-and block are in their radially inward position. The spacing of the lugs is such that the pin end I32 may pass therebetween and, by engaging the then embracing walls of adjacent lugs I33, mechanically connects the barrel units together. Since the driving torque is often high and frictional resistance of the pin end I32 and the lugs I33 would defeat the operation of the centrifugal force, the pin is mounted for free rotation about',its own axis so that. it is in rolling engagement with. theside walls of the lugs I 33 with which it may be in cooperation at any given instant.

For mounting the pin in this manner, it is proand 'pin may be displaced readily by the oentrifu- 1 gal actionof the comparatively heavy block I21. It must be noted that the radially movable part of the clutch is carried in the higher speedof the two cooperating barrel units, as the main object for this particular operation, is to disconnect the higher speed unit from the lower speed unit at the latter greatly reduces the efliciency of the smaller high speed unit. The low speed unit is not to be disconnected'from the high speed'unit when the low speed unit is dominant in supplying-the torque, as the high speed-unit does not appreciably affect the low speed units. On the descending scale, the terrific torque pressures are such that even rolling frictional engagement between the pin end I32 and lugs I33 is greater than the centrifugal force so that driving connection from a larger stage unit to the impeller shaft through the medium of the smaller stage units is assured.

Referring next to Figs. 11 and 12, a. slightly different clutch arrangement is illustrated. In this form the larger barrel unit I40 and smaller eration. A heavy flange portion I42 is provided $0 barrel unit I4I are shown in position for coop-- on the smaller unit and overhangs a correspondin'g hub portion l43 on the larger unit. The hub I43 of the large unit is provided with a number of hemi-spherical recesses I45, having their diametral planes at the surface of the hub. The flange I42 is provided with a plurality of radial bores I46 of substantially the same diameter as the recesses. Suitable balls I41 or other floating lugs are disposed in the bores I46 and are reciprocable radially therein, these balls being partially accommodated in the recess I45 and partially in the bores I46 for connecting the barrel portions together. Under the action of centrifugal force, however, the balls are thrown radially outwardly in the bores I46 and thus disconnect the barrel portions, from each other. Here again the speed at which the disengagement is to be effected may be positively and accurately controlled by suitable springs I48 contained in the bores I46. The springs I46 are operatively interposed between the balls I45 and suitabe plugs I49 in the outer ends of the bores, so as to urge the balls radially inwardly into the seating position in the recesses I46 while permitting yielding resistance to movement of the balls radially outwardly under centrifugal forces. Thus, in'those instances wherein such action is desired, each stage unit may be operated separately from the larger unitsof the group.

Referring briefly to the operation of the structure of Figs. 1 to 6,-lowest speed is obtained by setting all units to full stroke. The stroke of the larger unit is then reduced, and, due to its large fluid capacity ratio, the smaller units increase in between it and the small unit being such as to maintain substantially constant efficiency and power delivery during the change. Finally, the small unit alone is operating, and overspeed is then obtained by reducing its stroke.

In order to better appreciate the results and advances in the art accomplished by the present invention, the numerous governing complex and co-related problems of which the solutions are provided hereby and the manner in which prior structures are deficient for these purposes will be briefly delineated for purposes of comparison.

Referring to Fig. 22, a graphical representation of the relation of horsepower output and speed sought to be effected by a hydraulic motor embodying the principles of the present invention is disclosed, specific numerical values being used for greater clarity in illustration. In this instance it is assumed that a 100 H. P. hydraulic motor is used and is connected to a suitable reversible variable delivery 100 H. P. pump, so cooperated, in turn, with a suitable prime mover as to deliver to the motor the necessary horsepower in the form of pressure fluid. The motor is thus to deliver a constant horsepower within speed limits of 30 R. P. M. to 1200 R. P. M. for example, a ratioof 1 to 40. In addition, both an overspeed drive of 100% and an under-speed drive of 50% are .to be provided andare to operate at reasonable efiiciency, though, of necessity, above and below thewide rated limits, the horsepower delivery will diminish proportionately to.change in speed beyond the rated limits.

Assuming the horsepower and speed to be designated respectively by the coordinates of the graph of Fig. 22, between speed limits of 30 to 1200 R. P. M., a constant horsepower delivery cycle of 100 H. P. at the rated speed ratio of 1 to 40, is illustrated by section A of the graph. Below the rated minimum speed of 30 R. P. M., the horsepower will diminish gradually as the speed decreases to about R. P. M. or 50% underspeed, the efilciency decreasing proportionately to the degree of under-speed but being sufliciently high for most purposes during the under-speed period. Above the required maximum rated speed of 1200 R. P. M., however, and at slightly diminished elficiency due to the over-speed the speed increases to about 2400 R. P. M., an overspeed of 100% due to the characteristics illustrated in Fig. 27. The horsepower decreases at a substantially constant rate and in a direct proportion to the amount of over-speed as at this speed it is passed far beyond its critical range,

. but the efiiciency is sufliciently high for economical over-speed driving. Power cost and increased wear of the motor render it undesirable to exceed the low speed and high speed limits described for long periods of operation but for short period of operation the under-speed and over speed will operate effectively and with no damaging results. These limits are designated B and C respectively on the graph of Fig. 22.

The great necessity of a motor having constant horsepower characteristics for a large range of speed ratio is emphasized by insistentand permanent industrial demand, now long ex stent but not heretofore met, or even approached, though many attempts have been made so to do.

When, with these constant power characteristics, there is combined the characteristics of speed change at infinitely small increments and decrements throughout the entire range of rated speed and over and under speeds, it is apparent that neither mechanical nor hydraulic devices of the prior art can approach the operation.

In addition, it should be noted that in cost of production, durability, weight, overall dimensions and dependability, the new transmission must be not only equal to'prior structures but it must be superior thereto if demand for it by the industry in preference to greatly refined mechanical transmission is to be expected.

Considering the problems presented, there is illustrated in Fig. 24 one of the basic concepts underlying the present invention. The graph therein discloses certain functional relationships between torque and speed of a variable speed,

constant H. P. motor, assumed, for clarity, to deliver a constant power. With the abscissa representing speeds and the ordinate representing torque in foot pounds, for instance, it is apparent that as the speed increases, the torque decreases and, as the speed decreases, the torque increases. This discloses the fact that delivery of constant power at variable speed necessitates a large torque as the speed approaches the lower rated limit but a proportionately less torque at higher speeds. In fact, both speed and torque approach infinity in inverse relation to each other very rapidly, each at the extremely low limits of the other, the ordinate and abscissa being the asymptotes of the curve. I

With' this relationship in mind, a very important fact, the existence of which has not heretofore been recognized, should be noted, as it is a basic and controlling principle of efficient hydraulic transmission, namely; a constant power requires a motor structure commensurate with the maximum torque to be transmitted at the low speed and proportionately larger than a motor for the same power delivery at higher speed operation. Two factors must be considered, first a high speed motor for efliciency must be light and small, but a light and small structure is incapable of withstanding the heavy torque which is necessarily imposed at low speed operation. The torque required at low speed operation will collapse and utterly destroy a unit which is designed for eflicient high speed operation wherein it need withstand only a very small torque. On the other hand, a large motor structure cannnot be efliciently utilized at high speed because its efliciency and delivery drops rapidly beyond its critical speed, which is much lower than the high speed required. Furthermore, for higher speeds, its efliciency decreases because of shortened stroke. Consequently, constant. power could not be obtained with a larger unitv due to its inability to operate efliciently at the higher speed. It follows, therefore, that eflicient transmission at constantpower necessitates a small unit for the higher speed ranges and a large unit for the lower speed ranges. If this rule is notadhered to a structure. will result which willeither become inoperative and be destroyed under high torque stresses resulting from low speed or will operate at such low efliciency at high speed as to be of no practical value, all of the power being utilized in overcoming losses in the structure itself. Briefly, then a light structure required for high speed would collapse at low speed whereas an unduly heavy structure capable of withstanding the torque at low speed would have no useful delivery at high speed. The curve of Fig. 24, therefore, may be said to represent not only a torque speed relation but a speed size relation wherein it illustrates that a given size motor cannot develop the of the particular hydraulic reducer.

.at the lower speeds.

duction in the speed of the motor relative to the pump duetothe much greater fluid capacity of the motor with respect to the pump at a relatively slower speed of the motor but also for resisting and transmitting efficiently the much greater forces resulting from the greatly increased torque. Thus the fundamental requirements for larger capacity and accompanying speed reduction coincide with the requirements for resisting the greater stresses imposed by the torque These relations have not heretofore been recognized in connection with hydraulic speed reduction transmissions with the result that the efficiency of the latter have not generally compared favorably with the former except within the very narrow rated speed limits prior hydraulic speed reducers, in' order to operate throughout any appreciable speed range. necessarily had to operate at over-speed or under-speed throughout the major portion of the speed range required, with consequent diminishing horsepower output offsetting the advantages of uniformity and smoothness in speed change. Thus the prior structures provided only variable horsepower cycles.

This diminishing efficiency too narrowly limited the utility range due to the disproportionate power increase necessary for providing a starting torque. This, in turnpwas aggravated by poor mechanical designs including sliding frictional engagements of the reactance and c osshead actuating parts. Much more power i required to overcome static friction tostart a hydraulic motor of prior designs than is required to drive the motor against dynamic frictional resistance.

.Consequently, in prior designs, though suflicient power is present to operate the motor at the low speed safe limit safeiy ff thefmotor is stopped, it could not be started again by' this same power, but the safe power limit would have to be exceeded greatly to overcome the static resistance. The entire range, therefore, is limited by the safe power limit required for starting the motor and the lower operating speed limit must be retained considerably higher than -would be necessary other than for this phenomenon. These maximum and starting torque conditions are necessary for most applications of power transmission and cannot be ignored.

Another equally fundamental and unexpected fact is disclosed by Fig. in that torque, size and v speed relations do not vary in simple direct pro- In fact, the

ciency of a unit in function of its horsepower output and also of the output of various size units. The pressure and speed are assumed equal in all instances. This graph discloses that for a larger unit, the efliciency is greater than for a smaller unit, a fact not heretofore realized in connection with hydraulic motors. vThus if it were possible to provide a single large motor, both operable within the wide speed range requiredand capable of delivering 1000 H. P., such motor would'be the most desirable, as its efficiency would be 98%. But such a large unit alone could not provide the large range of speed ratios, due to the rapid decrease in efliciency accompanying a decrease in stroke, which decrease is necessary to cause the increase in speed. This relation is shown in Fig. 25 wherein the abscissa of the graph represents the eccentricity of the motor and the ordinate represents the efficiency. It should be noted that the efliciency curve is generally parabolic, being substantially constant down to a certain point, and thereafter the efficiency decreases rapidly and at a highly accelerated rate as the eccentricity approaches the lower limit. This phenomenum results from the fact that an increasing disproportionate part of the entire power becomes necessary to overcome pressure and friction in prior designs. This increase is so greatly disproportionate as the stroke is greatly reduced-that substantially all of the power is not only wasted in overcoming frictional and pressure resistance and drag but is so applied to the parts of the motor as to damage them and increase this very frictional resistance it seeks to overcome, and soon locks the motor.

As pointed out in my copending application,

Serial No. 7,809, filed February 23, 1935, however,

the efficiency of a smaller motor does not decrease as rapidly as does that of a larger motor of the same design operating at equal fluid capacity provided by short strokes or low eccentricity of the larger motor, as at such capacity the smaller motor is operating at a greater percentage of its maximum stroke.

In Fig. 26 it is shown that for a given power and speed, which are assumed constant, the efficiency of themotor varies as the size is changed. Representing the efliciency by the ordinate and the size per unit horsepower, or specific size, by the abscissa, it is seen that the relation curve rises from zero to a maximum, designed by ordinate n max, as the size increases, and then drops off as the size additionally increases. ,This maximum occurs for the smallest size commensurate with the highest efficiency for thegiven conditions, and may be referred to as the "critical size.

Next, certain controlling relations exist between efliciency and the ratio of stroke to cylinder diameter in a given size motor. As illustrated in Fig. 25, motor efliciency in a given motor and the eccentricity, or one half of the stroke, are definitely related.

As illustrated in Fig. 28, there is also a definite relation between efficiency on the one hand and the ratio of stroke to cylinder diameter on the other. However, the cylinder diameter remains constant while the stroke or eccentricity is varied to change speed and consequently the ratio of stroke to cylinder diameter varies. This variation also will affect the efficiency of the motor. The curve shows that maximum efllciency results only at one certain stroke-cylinder diameter ratio. This point rnay be termed "critical requirement.

ratio. A given design of pump or motor will operate most emciently whenits structure meets this critical ratio and will operate at high efllciency if the structure approximately meets this Thus all of these problems are inter-related.

Referring again to Figs. 23 and 25, the three stage units of the present motor are of differlar low speed. Also the greatest fluid capacity is provided. The units m and n2 do not operate at the, higher efficiency of which they are capable were they operated at higher speeds. However, when the capacity relations of the stages are considered, it is seen that only 94 of the output is providedby the unit 1 1 and only by the unit z, being provided by the unit 173. Thus the largest unit dominates greatly. Since its efficiency is high, the total efficiency of the combination is high and the losses at a minimum.

- One manner of increasing the speed gradually from the extreme low speed is to gradually decrease the strokeof the largest-unit m. This decrease need only be within-a range at which the mains high. Having accomplished this,"the. step may be repeated so that all of the operation is transferred to the smallest unit 51. It should be particularly noted that the driven shaft is carried by the smallest unit. Consequently, by disconnecting entirely mechanically each of the larger units in turn from the smaller unit, their drag and pressure'friction do not affect it at its higher speeds. .Instead of this operation the following steps may be followed.

With all units operating the lowest speed is maintained. This speed may be increased by decreasing the stroke of 1 1 to zero and then 1;: so

that-1;; alone is operating. Further increase may be obtained by decreasing the stroke of s until its highest speed commensurate with the high efliciency iseffected, for example, at about one half stroke. Beyond this point theunits m and 1;: may be operated to full stroke and the eccen-.

tricity of 1 3 reduced correspondingly so that the unit 1,: dominates. So little of the fluid capacity at this time is passing through 1;: that even with its lowered efliciency the total efficiency of the motor remains high. The stroke of 1 may then be reduced to zero, the entire capacity being utilized at higher speeds than units 1 1 and m. It is noted that as the speed increase is eflected, the efliciency of the units m and 1;: has increased,

a la na Next the eccentricity of m may be reduced to about stroke with a corresponding increase in speed of we. The next range is efiected by reducing the stroke of 1;: within efilcient limits of operation. Toward the lower limit of the unit 1 1 is again connected in the line and the stroke of m gradually reduced tobring m into its operating range of efliciency. Obviously, a veryslight change in 1;: due to its much larger fluid capacity than m causes a great increase in the fluid capacity to m while more greatly decreasing the efiiciency of 1 2'. Thereupon the eccentricity of 1 2 may be rapidly decreased, i becoming and remaining dominant until 1 2 as well as m is at zero eccentricity and mechanically disassociated from 1 2 due to the higher speed and the clutch mechanism provided. For over-speed, though with a decrease in efficiency, the eccentricity of m is reduced.

Another system of operation which requires only simple connections for shifting is to start all of the units at maximum eccentricity. After starting 11: is operated by varying its stroke to increase its speed. Due to its much larger capacity than the other units the speed will increase so that m andm are operating at high efilciency and dominating while-m is still oper-' ating within its higher efficiency range. Thus.

the losses of emciency due to the shortened stroke in m is replaced by the increased emciency in m and 112 at the higher speeds, 1 2 may become dominant; This speed increases until 1 1 ahd 1 2 are mechanically disconnected from 173 and the eccentricity of 1 3 is then rapidly reduced to zero. This same operation is repeated until m is the only unit operating.

Thus then through a large range of speed, operation is efiected at or near peak emciencies and the ,eiliciency curve of the combination approaches the 100% line as an asymptote, Consequently, all stages operate for their dominating periods at the flattened crests of their curves, each being brought to maximum efiiciency while the operating unit remains substantially at maximum efliciency.

The combined horsepower, therefore, while not a straight line parallel to the abscissa as in Fig. 22, will very closely follow such a line by a continuous series of flat reverse arcsso close thereto as to be for all practical purposes, identical. The graphs curves of the individual units, though not defining a straight line or so fiat a curve, overlap in the direction of the abscissa so that the algebraic sum thereof provides the substantially flat composite curve. With each stage an economical design"- and so related to the others, the efliciency is necessarily high.

With these characteristics in mind,-it will be noted in connection with the graphs, that a single -large unit could not effect the results, as the efliciency decreases so rapidly near the upper speed limits due to lowered eccentricity and accompanying decreased stroke-cylinder ratio and higher speeds above the specific speed of the large unit. For example, if the motor of Fig. 25 is a 1000 H. P. motor at full stroke, at about stroke, the emciency is only 50%, the horse-.

performs most efllcientlyatthe speed for which designed, known as the "critical" speed. Consequent y, to maintain a constant horsepower throughout any appreciable range of speed, it is necessary to provide a plurality of units, each of an economical design for a different critical speed; These units must be so combined as to operate simultaneously or successively, and while the stroke is being adjusted, in such a manner that each unit dominates the power output of the combination in the range of its critical speed and economical design and these ranges must overlap at regions of reasonable efliciency.

It is again pointed outthat constant horsepower at variable speed results in greater torque, stresses, stroke, size of plungers, plunger heads, guideways, barrel and other structure at lower speeds but less torque, stroke and lighter and smaller structure at the higher range where ceritrifugal forces become a controlling factor, and with gradations inbetween. Such a structure has not heretofore been provided. Instead, at tempts have been made to solve this broad problem by a plurality of units of equal size. For the reasons recitedabove, equal size units will not effect the result. As. an example, if four units of 250 horsepower each were used and operated simultaneously to produce an expected 1000 horsepower, since no one of them is of "economical design', for the slower speed resulting from use of the total capacity of the pump, the

expected 1000 horsepower would not be produced.

' Further, the strength and large stroke most emcientfor the lower speed and provided by a single large unit would be lacking.

Where a single large unit may well operate at 95% efliciency at full stroke, each small unit would operate at 85% efficiency, for example, at full stroke. But this would not render the combination of the four units operable at 85%, unless all were operating together at full stroke. It

must be remembered that in such structure the four units are mechanically interconnected and if any stages are set to neutral or such reduced stroke, the others must overcome the hydrostatic load. efiects creating frictional resistance and wear in the former. Thus the ineflicien'cy of each is added. The same is true above the critical speed of each unit. I

Since the units are of equal size, no one of them dominates the others at the difierent speed Therefore, there is no dominating high eiliciency which raises the efliciency of the entire motor. Infact, both a single large unit'or multiple equal size units are insumcient for ac--? complishing these results as beyond a certain range of speed they become inoperative, the latter because the neutral stage will consume the energy or power of the working stages which 'must be driven bythe working stage at an extremely low eccentricity. Even the working stage operates at low efficiency which .decreases rapidly as the stroke decreases.

In the equal stage units of the prior art, the

mechanical and hydraulic braking effects and losses in the neutral stages will reach an. amount equal to the power developed by the short stroke of theactive stage atwhich point the transmission or motor will stall. At'this point, the mere introduction of more pressure by the pump will Here a vast difference in motors and pumps should be noted. Ina pump, regardless of how much the stroke is shortened, the pump will remain operable due to the fact that at the shortened stroke less fluid is pumped .cause.

and the total power of the prime mover can be utilized in creating greater pressure at less volume and in overcoming the frictional resistance at low eccentricity. In a motor, however, once it has stopped at low eccentricity, the dynamic friction is replaced by static friction which, as is well known, increases the resistance many times, as high as ten to one hundred times. Once this static friction has become effective, an increase with the result that suflicient eflective torque may be provided to overcome the resistance from this The equal small units, therefore, produce a less desirable result than a single large unit as the single large unit would operate at least at the low speed and within a certain effective range, whereas the equal small units cannot. This is especially true wherein the coupling between the plungers and reactance is a sliding coupling in which static friction is developed to 'a very high degree when the structure is used as i a motor.

For these reasons the anti-friction coupling must withstand terrific radial thrusts. Therefore, sliding friction between the plungers and reactance is eliminated. Even in pumps, however, at such slight eccentricity and high frictional forces, the entire power of the prime move er is often converted intc the mere maintenance of suflicient .capacity to replace slip fluid resulting but, in such instance, there is no actual delivery of working fluid to the motor. Thus a change in structure may also increase the eiiiciency of a pump which wouldbe operable even without such change, whereas the same change in a motor may be controlling as to operativeness and inoperativeness, certain kinematics being present in the operation of the structure as a motor which are not'present in the same structure when operating as a pump.

In the structures heretofore described it should .-be noted that where the barrel is made in one piece, the working stages must drive the neutral stages and overcome any frictional resistance of i the latter, because the pressure is still acting in the neutral stages to force the plungers tightly against their reactance. If these connections are progressively become operative in their peak range of efficiency, are provided, so that the total result is a substantially constant peak efficiency throughout the entire range of operation.

In the latter instance, the large unit necessarily operates at slower speed and does not become disconnected by centrifugal forceuntil the next sucof reversible rotary radial plunger stageunits,

each unit comprising a, barrel having a. set of radial cylinders, plunger assemblies respective to the sets of cylinders and reciprocable therein,

reactance means for the assemblies, valve means for the sets of cylinders, clutch means operatively interposed between the adjacent barrels of the units for mechanically connecting the said ad- Jacent barrels-for rotation together in either direction of rotation within predetermined rotational speed ranges, and for disconnecting the said adjacent barrels of said units consequent upon a predetermined speed of one of said ad- Jacent barrels. a

2. In a multi-stage hydraulic motor, a plurality of reversible rotary radial plunger stage units, each unit comprising a' barrel having a set of radial cylinders, plunger assemblies respective to the sets of cylinders'and reciprocable therein, reactance means for the assemblies, centrifugally operated clutch means operatively interposed between the barrels of adjacent units for mechanically connecting adjacent barrels for rotation together within predetermined rotational speed ranges and for drivingly disconnecting the barrels respectively from certain adjacent barrels consequent upon a predetermined speed of one. of the ldlacent barrels.

3.- In a multi-stage hydraulic motor a plurality of stage units, each unit comprising a barrel means having a plurality of radial cylinders, means mounting the barrels of said units for rotation independently with respect to each other, radially reciprocable plungers for said cylinders respectively, reactance means for said plunger assemblies respectively, valve means in valving cooperation with said cylinders, a rotatable shaft common to and associated with said units for rotation thereby, said units being of different overall dimensions with respect to each other, and in a proportion providing economical design in a continuous speed range successively dominated by the units in the order of their size,

and means adapted to provide driving connection between adjacent barrels at certain relative speeds thereof,

4. In a multi-stage hydraulic motor a plurality of stage units, each unit comprising a barrel means having a plurality of radial cylinders,

means .mounting the barrels of said units forrotation independently with respect to each other, radially reciprocable plungers for said cylinders respectively, reactance means respective to the plunger assemblies, valve means in valving co- ELEK K. BENEDEK. 

